Field of the Invention
The invention concerns a process for the cooling of chunky or granular materials. Such a process and device are generally known from D4304675A1.
Processes and devices of this type employ, for example, the embrittlement or rigidification of industrial products, which are to be subsequently broken down. In particular, the breaking down and grinding processes are facilitated by the rigidification of the products, and thereby the energy requirement for this type of process is minimized.
It has been found particularly advantageous to employ such a cooling in the breaking down of multi-component products such as, for example, electronic waste material. Electronic waste material is comprised of very diverse materials, in particular of metals and plastics, wherein frequently the later are at least partially subjected to halogenation for the purposes of fire-proofing. A recycling of this type of diverse material requires first the unlocking thereof, that is, a breaking down of the binder material. As a result of a strong cooling, for example to the temperature of liquid nitrogen, thermal tensions occur between the various materials, which simplify or facilitate their separation. On the other hand, the plastics become brittle while the metals such as, for example, copper or aluminum remain tough or tenacious, whereby a selective breaking down or fragmentation can be achieved. A third aspect thereof is that the cooling minimizes the production of dioxides and furans from the halogen-containing plastics and other halogenated components which would otherwise occur during the breaking down of electronic waste material following a strong warming of the material, which would damage the environment. The production of such environmentally damaging substances is substantially minimized or completely prevented in an inert gas atmosphere, for example, an atmosphere of vaporized nitrogen.
Known processes for the breaking down of multi-component articles such as, for example, expended batteries, are carried out in a continuous process and accordingly, very helpful processes or devices for cooling of the aggregate or joined materials to be broken down are likewise conceived for a continuous throughput of material and continuous operation (DE 43 04 675 A1, DE 41 06 599 A1). An experiment shows, however, that many multi-component composites, for example, electronic waste materials, can be selectively broken down (DE 195 18 277 C1). The plastic components of the electronic waste material are already strongly broken down after a short processing time, while the mostly metallic components have a substantially larger size (DE 195 18 277 C1). For recycling requirements, such a selective particle size reduction this is advantageous, since on the one hand, the necessary breaking apart between the various materials of the composite is achieved effectively, and on the other hand, the greater proportion of the metallic components are provided with a large particle measurement which is comparatively simple to separate. The selective breaking down requires, however, different from conventional processes, until achievement of a somewhat uniform particle size reduction of plastic and metallic components, a batch-type, that is, a discontinuous operation, in which the composite material is only subjected to the breaking down process for only a defined period of time and then with still strongly divergent differential particle size measurements is removed from the breaking down device. For the cooling devices of the proposed breaking down devices there is, economically speaking, in comparison to the conventional cooling devices, a batch-type operation just like the breaking down device, and thus discontinuous operation, thereby saving energy and cooling materials in comparison to the continuously operated cooling device, since cooling is not carried out beyond an optimal period of time.
Beyond this, consideration must be given to the strongly varying temperature dependencies of the breaking down process for the various composite materials. Therefrom there results on the one hand a requirement that for the carrying out of an adequately selective breaking down a homogenous-as-possible temperature distribution is desired within the particle mixture to be reduced in size of the various composite materials. Otherwise, it can occur, that various materials do not show the desired variation or differentiation in particle size reduction relationship, that is, a selective breaking down, but rather on the basis of the varying temperatures show a similar breaking down relationship and are broken down non-selectively. On the other hand, a non-homogenous temperature distribution within the particle mixture to be reduced in size for the various composite materials leads to an uneven separation of the various composite components, whereby a subsequent sorting or separation is substantially complicated.
A further essential criteria for the realization of a sufficiently selectivity in the reduction of a certain amount of composite materials is comprised therein that the total amount of the composite material is subjected for a common, defined period of time for the size reduction requirement. In order to make this possible, the entire amount of the composite material must be fed to the size reduction device at one period in time or at least within a short period of time. This requires, besides the discontinuous operation of the upstream cooling device, above all a discontinuous emptying out.
In DE-A-2550958 a process for recycling of expended materials is described, which includes a process step of cooling the expended materials, wherein the old material is discontinuously supplied in vats to a closed, isolated cooling chamber. In the cooling chamber the vats are over sprayed with a low boiling, liquefied gas until achievement of a predetermined temperature and in this manner are cooled. The temperature is measured outside the vats. No indication is given as to the design of the vats. After cooling the vats inclusive of the material to be recycled are removed from the cooling chamber and then the vats are emptied of their material to be broken down.
This process has numerous disadvantages: since the temperature is measured outside of the vats, in order to insure the attainment of a homogenous temperature distribution in the material being recycled this must be cooled for a significantly longer period of time than in the case of a direct temperature measurement within the material being recycled. This applies particularly, when closed vats are employed so that the cooling must occur through the walls. If on the other hand open vats are employed, then a large part of the fluidized gas is carried away during the removal from the cooling chamber. Beyond this it is also necessary that in addition to the material being recycled also the vat must be cooled, as a result of which the requirement for cooling medium increases unnecessarily. Besides this there is the energy requirement for the filling of the vats with the material being recycled, and further for the filling of the cooling chamber with the vats, as well also for the removal of the vats from the cooling chamber and for the transport of the vats to the breaking down device. Accordingly this process has a high requirement for time, energy and cooling media with small homogeneity of the temperature distribution in the material being recycled.
In GB-A-1482908 a device for the supply and cooling of granular material is described, which includes a cooling tank and a there above positioned wheel sloose for the filling thereof and the upper part of the cooling tank there is secured an indicator for the condition for filling. This serves to stop the feeding of material via the wheel sloose as soon as a fill level indicated thereby is achieved. In the lower part of the cooling tank there is provided one or more inlets for a low boiling, liquefied gas. No details are given regarding the carrying out of the process in this cooling device.
This device exhibits a number of disadvantages: it indicates two conceiveable possibilities for the carrying out of the process which this cooling device. Either via the wheel sloose and the fill indicator a determined (preset) amount of the granular material supplied and thereafter is cooled. Alternatively the cooling occurs already, while material is still be introduced via the wheel sloose. In the first case the time requirement is comparatively high. In the second care the duration of the cooling of the material, which is introduced first, is longer. Therefrom there results an inhomogeneous temperature distribution or a higher time requirement until achievement of a uniform temperature distribution. In general an inhomogeneous temperature distribution is more likely to be expected, since the lower boiling liquefied gas or the supply for the low boiling liquefied gas is situated in the lower part of the cooling tank and this is filled up to the upper part of a level-sensor. Beyond this, this device can only inadequately respond to the demands of various materials (composites, coating thicknesses, insulation value, etc.) or subsequent processes (breaking down processes, desired particle sizes, degree of unlocking, etc.), since the fill amount of the cooling device is predetermined by a level sensor.